Condition responsive valve control circuit



Feb. 10, 1953 s, sTAEGE 2,627,875

CONDITION RESFONSIVE VALVE CONTROL CIRCUIT Filed Feb. 12, 1948 3 Sheets-Sheet l 4 E firs-Magi? ATTORNEYS Feb. 10, 1953 s. A. STAEGE CONDITION RESPGNSIVE VALVE CONTROL CIRCUIT Filed Feb. 12, 1948 3 Sheets-Sheet 2 I INVENTOR I45 a 512 6,

7?? Z hflM TTORNEYS Feb. 10, 1953 s. A. STAEGE 2,627,375

CONDITION RESPONSIVE VALVE CONTROL CIRCUIT Filed Feb. 12, 1948 s Sheets-Sheet s y lzz/ lmm IE2 e E i- Z MI INVENQTTDR WM ATTORNEYS Patented Feb. 10, 1953 OFFICE CONDITION RESPONSIVE VALVE CONTROL CIRCUIT Stephen A. Staege, Hamilton, Ohio, assignor to The Black-Clawson Company, Hamilton, Ohio,

a corporation of Ohio Application February 12, 1948, Serial No. 7,7 61

14 Claims. (01. 137-723) This invention relates to paper manufacture, and more particularly to controls adapted for use in connection with machines or apparatus for the manufacture of paper.

One of the objects of the invention is to provide a control device adapted for use in paper manufacture which is simple and rugged in construction and which will provide precision control over a desired pressure condition such as the liquid level in a machine head box, screen collecting box, cylinder machine vat or like installation.

Another object is to provide a modulating control device of high sensitivity for maintaining a predetermined pressure condition which is effective to. cause a correcting action proportional to the change in the condition to be maintained and which will accordingly maintain a desired condition substantially without over-travel.

An additional object is to provide such a control device capable of effecting a correcting action which is not continuous but is intermittent in accordance with a predetermined time cycle and with which the number and the duration of the correcting actions in each cycle are caused to vary in accordance with the magnitude of the change in the liquid level or other condition to be maintained to give an aggregate correcting action substantially proportional to the total change in condition.

It is also, an object of the invention to provide such a control device which is effective as a resulator oi'high sensitivity for normally correcting relatively small errors with substantially micrometer precision and which is also capable of rapidly:

correcting for large scale variations such as the changes-in liquid level or pressure which occur when changing paper speeds or under other conditions which do not require precision control.

A' further object is to provide such a control;.

de-vice which possesses a high degree of sensitivity capable of providing for precision control and which is so constructed that the movement of the parts movable in response to changes in the actuating forces is of such short extent and.

duration as to reduce wear to a minimum and to make possible a rugged construction having a long effective life.

Other objects and advantages of the. invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings, in which like characters of reference designate like parts throughout- Fig; 1 is aschematic view of the circulating iii and supply system of a cylinder type paper machine to which the present invention may be applied, showing the path of flow of incoming stock and collected White water as supplied to and discharged from the paper forming parts;

Fig. 2 is a circuit diagram illustrating the operation of controls utilized in accordance with the present invention for establishing and maintaining a predetermined liquid level in the vat of Fig. 1;

Fig. 3 is a view of the control device in side elevation with the front cover removed and with parts broken away and in section to illustrate internal construction;

Figs. 4 and 5 are sectional views on the lines id and 5-5, respectively, of Fig. 3;

Fig. 6 is a diagrammatic isometric view showing the arrangement of cross springs which provide a pivotal mounting in the control device;

Fig. 7 is a fragmentary stop view illustrating the means for adjusting the device to accommodate different liquid levels or pressures;

Fig. 8 is a fragmentary sectional view showing the membrane diaphragm utilized for screening suspended matter from the control device; and

Fig. 9 is a somewhat diagrammatic fragmentary view showing the cam which operates certain of the electric contacts in the control device.

Referring to the drawings, which show a preferred embodiment of the invention, Fig. 1 illustrates somewhat schematically the circulating system for a cylinder type paper machine. The vat i9 is shown as having the vat circle ll with the rotary forming member or cylinder mold l2 mounted therein. A tapered vat inlet :5 supplies the incoming stool: to the vat, the usual mold slice [Sand adjustable rotary slice ll being provided as desired. The vat has an overflow compartment 2d at its side opposite the inlet 15, and an overflow slice is indicated at 2!.

The White Water is Withdrawn from the vat through pipe 22 and is fed through conduit 23 to the white Water pump 24, new stock from the usual regulating box being introduced into con duit 23 from pipe 25 directly ahead of the pump 2 The discharge of the white water pump is supplied through conduit to a suitable screen 32 from Which the screened stock passes through conduit 33 to a conduit 35 which also receives the discharge from the overflow compartment 20. A branch conduit 3'6 provides for the return of a portion ofthe White water directly into this conduit 35. p

of casing E i.

A circulating pump 48 delivers the stock from conduit 35 through a conduit 4! which is branched at 42 to supply stock to a pair of tapered counterfiow conduits 43 and 44 which are shown as of the construction disclosed in Patent No. 2,347,717 assigned to the same assignee as this application, and which are provided with a common discharge orifice 45 through which the stock is discharged into the tapered inlet passage 15 and thence into the vat.

In order to maintain a predetermined level of liquid within the vat, an adjustable valve 59 is positioned at the lower end of the overflow compartment 20 to control the discharge from compartment 20 to the conduit 35, satisfactory results having been obtained with a plate type gate valve in which there is no bonnet to collect stock or a Saunders type rubber diaphragm valve. Provision is made for reversible power operation of valve 50, a reversible electric motor being shown as operatively connected to cause rotation of valve 50 as indicated diagrammatically at 52, and a control device indicated generally at 55 provides for intermittently operating the motor 51 in accordance with change in the liquid level within compartment 20 to maintain a desired level condition within the vat. To provide for adjusting movement of valve 50 through small increments, the drive from motor 5! should include a large reduction ratio.

Referring to Figs. 2 to 5, the device 55 includes an element 56 capable of developing pressure in accordance with changes in the desired condition to be maintained. A conduit 51 is connected with the interior of compartment 253 at 58 to transmit to element 56 the changes in pressure within the compartment produced by sure plate 56, the latter being shown'as transparent to facilitate observation of the operating parts of the device. The casing 64 may be mounted at any convenient location relative to the paper machine by means such as a pipe or bracket 51, care being taken when the device is used to control liquid level to assure that the device is at such height relative to the vat or other container to be controlled that the pressure responsive bellows 58 will be sufficiently lower than the liquid level within the container to be under some degree of static pressure at all times.

A beam 7B is pivotally mounted within casing 64 by means of cross springs for limited movement in response to changes in pressure within the vat. Referring to Figs. 3 to '6, beam H1 is welded or otherwise secured at one end to a block H which is secured by bolts 72 and a plate or strap 73 to one flanged end 74 of a Z-shaped spring 75. The other end ?6 of spring 75 is similarly secured by bolts l7 and a plate or strap 78 to a block 3t secured by bolts ti to the end wall Blocks 7| and 8B are further connected at each end by a pair of fiat springs 82, which are secured thereto by plates or washers 83 and bolts 84, and these three cross springs and 82 thus provide a pivotal mounting for beam "iii allowing the beam to move with relatively low' friction and relatively minute spring losses and providing high sensitivity in use.

Beam Iii is connected with bellows Si in such manner as to provide for pivotal movement of the beam in response to changes in the pressure eiiective on the bellows. Referring to Fig. 3, bellows Ed is shown as a metal bellows having a large number or" convolutions and arranged in cup 59 for pressure on the outside thereof, a bellows of this type having been found satisfactory for control of conditions such as liquid level or fluid pressure because it possesses high sensitivity and also because each convolution is subjected to relatively small deflection in use, thus reducing wear on the device and also iizing its resistance to deflection and the attendant loss in sensitivity. In addition, with this cup type of bellows the center of gravity at a sufficiently low position to give desired stabnity under pressure.

The cup bolted or otherwise secured within casing and is provided with a nipple 35 or like member for connection to conduit 57 as shown. Means such as a petcock 3? is provided at the top 853 of cup 5o permit escape of air while the cup is being filled with liquid, thus providing for complete absence of air in the bellows system so that any variation in pressure in compartment 2% will be transmitted more quickly to the bellows than would be the case if air or another gas were present in the cup to cushion such pressure changes, and all joints in cup 59 as well as the connections to conduit El are preferably soldered or otherwise treated to assure a liquid type seal. This absence of air and the small movement required for bellows 60 provide for relatively negligible volumetric movement of fluid through conduit satisfactory results having been obtained utilizing A; inch pipe for this conduit.

When the device is used for maintaining liquid level in connection with a paper machine or in other installations where suspended material is present in the liquid being controlled, means such as a membrane diaphragm may be provided for preventing such suspended material from entering the bellows cup 59. Fig. 8 illustrates such a diaphragm $2 as mounted at the point of connection 53 of conduit 5? to compartment 28. As shown, diaphragm is is clamped between a metal ring SI and a plug 92 which is secured in water tight relation in the hole 58 in the side wall of compartment 28. A hole 93 in plug 92 is provided with a nipple 94 or like member for connection to conduit Plug 92 is also provided with a pipe fitting 55 having a removable closure plug 5 5 for filling conduit cup 6! and the space between diaphragm 9d and plug 92 with water or other clear liquid.

With this arrangement, fluctuations of pressure Within compartment 28 resulting from change in the liquid level therein are readily transmitted through diaphragm so without affecting the sensitivity or accuracy of the device. If desired, conduit 57 may be provided with a valve or small restriction to damp rapid fluctuations of large magnitude in the system, as indicated at 9? in Fig. 3.

The upper end of the bellows 55 is soldered or otherwise sealed to the cover 33 of cup 5e, and for use of the device for liquid level control the interior of bellows Ed is open to the atmosphere through a hole 95 in cover 333. A rod lei? is secured to the bottom of bellows and passes through hole 38, and its upper end is secured to a clevis 181 which in turn straddles beam .39 and is piv otally connected thereto by a pin 582. Changes in pressure within cup it. thus result in expansion or contraction of bellows 6d, and such movement of the bello -'s will be transmitted through rod I and clevis' IIII tocausenpwardor downward movement of vthefreezend of beam 10. Stops Illareprovided at the opposite end of casing 64 fromithe pivotal mounting of the beam. to limit this movement of the free end of the beam, satisfactory results having been obtained .with these stops arranged to permita total range of movement of approximately-.25 inch for the free end of thebeam, thusminimizing'the total deflection of the cross springs at the pivotedend of the beam and correspondinglyreducing thestressesthereon in .use.

Adjustable means are provided forregulating beam III to balance difierent pressures on bellows 60. in order to accommodate thedevice to the control ofdifierent levels of liquid-or other conditionsto be maintained. A'threaded rod or adjusting screw III] is rotatably supported at one end in an ear or lug I II mounted on the free end of beam III, this end or" screw III] being-of reduced diameter and being held. against axial movement relative to lug II I by collar II2 as shown in Fig. 3. The other end of screw IIO.is supported in ayoke or lug I I3 mounted adjacent the pivoted end of. beam 10, and it extends through a hole vI I 4 in the casing wall and is provided with a knurled adjusting knob I I5, this hole I It being of sufiiciently larger diameter than screw III] to allow for lateral movement of the screw-with beam I0. A short sleeve I I B is welded I to the outer side of the casing wall surrounding hole I I4 to guard against entry of water into the casing when the machine is being washed up after use.

A weight I26 is mounted for axial'movement with .respectto beamlil in response to rotation ofscrew i ll]. Referring to Figs; 3, 5 and 7, weight I is: slotted at I2I to straddle beam I8, and two boltsor pins I22 extend through'this slot'and ride on the beam to'support the weight I20 therefrom. The adjusting screw IISJ also traverses slot I 2I and it carries a nut'l 25 which fits within a'further slot I25 in weight I2Il'arranged at right angles to slot IZI andof such dimensions as to hold nut movement with respect to weight I29. Accordingly, when screw IIO is'rotated', nut I25will be caused to move axially thereof and of beam H3, thus causing corresponding movement of weight I25 relative to beam III to vary the amount of head which bellows 65 will support.

The device can thus be readily adjusted to, the control of a desired liquid level control or pressure or'other condition to be maintained, by appropriate adjustment of screw-I III to a position of weight I26 at which beam .IIl is'balanced in neutral position between the stops. I05 when the desired level condition is obtained. To facilitate this adjustment, a pointer I2? or other indicator may be mounted on weight I29, as by means. of one of the pins I22 as shown in Figs. 3 and 5, and a suitable scale may be etched or otherwise provided on the transparent front plate I56 of the casing, as indicated at I28, in cooperating relation with the pointer I21 for readily visible adjustchangeinthe liquid levelonother conditiontobe:

I25 against bothrotation and axial maintained, and the ,controlmeans'are also effective to vary the number and durationof oper ative intervals of motor5I in each operating cycle of the control means in accordance with the magnitude of the change or error to be corrected for. Referring to Figs. 3 and 5, a bar I is bolted or otherwise secured at I 36 to the free end of beam I0 and extends downwardly therefrom. This bar carries two vertically spaced circuitcontrolling members, shown as spring contacts I40 and MI, which are secured to a pair of yoke arms I42 electrically insulated'from each other and from bar I35 by blocks I43 and I44'0f suitable insulating material bolted to bar I35, the yokes I42 being riveted or otherwise secured to block I43 as indicated in Figs. 3 and 5. Thumb screws I45 are mounted in yokes I42 and engage contacts I I 40 and MI as shown in Fig. 3 to regulate the relative spacing between these contacts. Bar I35-is also shown as'pi'ovided with an outwardly projecting lug I45 providing a mounting for one end of a small biasing spring WI (Fig. 6) having its other end secured to the lower ofstops I05 and servingto reduce. extreme sensitivity ofbeam ID in cases where there is considerable turbulence or rapid variation in pressure.

Two additional circuit controlling members, shown as spring contacts I 58 and I5I, are mountedin the casing 64- in cooperating relationwith contacts I 30 and MI, respectively, and are movable with relation thereto. Referring to Figs. 3 and 5, the contacts I53 and I5I are securedto yoke arms I52 carried by a block or bar I53 of electrically insulating material which is secured to the base of casing 64 as by means of angle bracket I54. Thumb screws I55 are mounted in yoke arms I52 as shown in Fig. 3 and engage the contacts I 50 and !5I to regulate the relative spacing and tension of these contacts.

The twopairs of contacts 140-450 and I4II5I are connected in circuits controlling motor 5I, the contacts in each pair cooperating with each other to open and close one of a pair of selectively operable control circuits to motor 5I, as described in detail hereafter in connection with the circuit diagram in Fig. 2. The relative spacing of these contacts is so controlled that when the system is in balance, with the pressure on bellows just sufiicient to support beam III ;in its neutral position, neither pair of contacts will be in circuit-closing relation, but when the pressure on the bellows changes, the free end of beam It! will rise or fall correspondingly, thus carrying'one of contacts I40 and MI into circuitclosing relation with its cooperating contact I59 or I5I. In addition, means are provided for cont nuously moving contacts I56 and I5I towards andaway from their respective cooperating contacts I40 and'I II and also for continuously varying the extent or this movement of contacts I59 and, I5I to establish periodic operating cycles comprising a plurality of high points of different magnitude alternating with an equal number of low points, thus providing for varying the number of intervals in each cycle during which the active pair'of contacts will be in circuit-closing relation and the duration of each interval in accordance with the magnitude or" change in the condition to be maintained and hence the extent to which beam iii and contacts hit and MI have been ditions.

electric clock motor, mounted on the base of the casing 66 by a bracket I 63. The cam I60 is shown as octagonal, and each corner or lobe IE is arranged at a progressively diiferent radial distance from the axis of shaft I61. Thus referring to Fig. 9, the corner or lobe IBM is the highest of the eight high points of the cam, as shown by the dotted circle I53 which is centered on shaft MI and has a radius equal to the radial distance from the lobe "55a to the axis of shaft I SI. Each of the other high points or lobes I551) to I65h, inclusive, is arranged at a progressively lesser distance from the axis of shaft I6! and hence lies within circle I56. Satisfactory results have been obtained with each of these lobes or high points closer by 0.005 inch to the axis of shaft I6I than the adjacent higher high point, and the corner or lobe I65h thus represents the lowest of the plurality of high points of the cam and is 0.035 inch lower than the high point IfiEa, these dimensions being considerably exaggerated in Fig. 9 for purposes of illustration.

In use, the tension of contacts I59 and I5I is adjusted by means of thumb screws I55 so that both contacts will be in engagement With cam I66] at all times during a complete revolution of the cam. Each of these contacts will thus be caused to oscillate in periodic cycles corresponding to complete revolutions of the cam and each points of different magnitude, the low points being the points on each of the fiat sides I61 of the cam which are closest to the axis of shaft IBI. The length of each of these periodic cycles is determined by the speed of motor I62, satisfactory results having been obtained with the speed relatively low, for example 4 R. P. M. providing cycles of seconds duration, and with each cam lobe formed with a sharp peak as shown, the electric contact between a pair of contacts I4@I50 or I4I--I 5i can be controlled to as short an interval as A second. It is also to be noted that under some conditions of relative dimensions, one or more of the low points of the cam, for example the low point between the highest two high points, may be relatively higher than one or more of the lowest of the high points. In such case, however, the corresponding low point between such lower high points will be relatively still lower, thus maintaining the desired alternation between high and low points of different magnitude in each cycle.

Fig. 2 illustrates control circuits for operating the valve motor 5| in response to rising or falling movement of beam 75 occasioned by changes in the pressure effective on bellows 53. Motor Si is shown as energized from a three-phase source of power I15, and the motor is controlled through the provision of magnetic reversing switches I80 and IBI in a switch unit identified generally as I82. Suitable upper and lower limit switches I83 and I84 are connected in the circuit of each reversing switch so that the control circuits of the valve motor 5i will be deenergized when the valve reaches either of its limiting positions, thereby avoiding the possibility of damage to the motor or valve.

A control circuit for actuating the reversing switches I an and i8| is energized from the low voltage secondary of a transformer I85, and push button switches I96 and I9I provide for manual actuation of the respective reversing switches for rapid setting of the valve when the operator wishes to establish a change in the forming con- A manually operable reversing switch comprising eight alternate high points and low I92 provides for shifting the device betweenautomatic operation through the contacts I4fl-'I 50 or i4II5I and manual operation through switch I99 or IQI, these switches being readily grouped in a unit identified generally as I95. It will be understood that for manual operation it is necessary merely for the operator to shift switch I92 to the proper position and then to close either of the switches eat or I 95, and that the motor 5| will then continue to operate valve 5c in the selected direction so long as the switch is closed, or until the corresponding limit switch 583 or I84 opens.

In operation with the circuit arrangement shown in Fig. 2, the contacts Hit and MI are initially adjusted by means of thumb screws I45 to a relative spacin such that when the beam I0 is in approximately its neutral or balanced position, each of these contacts will be out of contact with its associated contact ISIS or I5! throughout the complete revolution of cam I63. This adjustment is preferably controlled to leave a desired margin, such as several thousandths of an inch, between each of contacts 54% and Iii and its associated contact I 58 or Ia'ii when the contacts in each pair are at their closest relative positions corresponding to the high point 565a on the cam. Accordingly, when the proper liquid level or other desired condition is being maintained, the circuits through both pairs of contacts H38I5t and l=.II5i will remain open, thus rendering motor 5! inactive and holding valve 5B in desired position to balance the stock entering and leaving the vat.

As soon as the liquid level in compartment 20 changes, for example if it rises, this will be translated into an increase in the pressure effective on bellows 66, causing the free end of beam it to rise and to carry contact MI in the direction of its oscillating cooperating contact I5I, the extent of this movement being substantially proportional to the magnitude of change in the liquid level. When this movement has been sufficient to carry contact I iI within the oscillating range of contact IEI as determined by the initial adjustment of contact It! by its thumb screw I 35, there will be electric contact between contacts MI and I5I, thus momentarily closing the circuit to the magnetic reversing switch 58! and causing momentary operation of motor 5! in a direction to cause valve 5K to open and thus to increase the rate of discharge from compartment 2%. The number of intervals of contact between contacts MI and I5I in each revolution of cam I50, and the duration of each such interval, are determined by the magnitude of change in liquid level in the vat and hence the extent to which contact I 4! has been raised, as will now be explained.

Referring particularly to Figs. 3 and 9, if cam I69 rotates in clockwise direction, during each complete revolution of the cam, contact I5I oscillates in a cycle comprising eight high points each .005 inch lower than the preceding high point in the cycle. As soon as contact I has moved within range of at least the highest of these high points, corresponding to the corner or lobe I 65a on the cam, the two contacts will touch and close the operating circuit to motor 5| at least during the instant when contact I58 is passing the cam lobe Ifia. If the change in liquid level has been fairly substantial, contact Iti may also move within range of some of the other high points on the cam, and each time the contacts close the circuit, the motor 5i will operate to cause acorrecting action in the system, thus producing a change in the pressure efiective on bellows GI] and 9 resultant return movement of beam id and contact MI to neutral position. However, the correcting action will continue only during the fraction or" a second when the circuit through con tacts iii an l is For relatively slight the correction produced by a ntervai of motor may be suiiicient to ret contact i i to its neutral positicn than nmit its engagement with contact i ii to a single, int val, or possibly to a single interval in one or two cycles, but for relatively larger changes in level, the movement of contact iii will carry it within. range of a plurality of the high points cam thus increasin the number of operative rvals of motor during each revolution of the It should also be noted that the contacts iii and SEE may touch r an instant before and oi the cam passes conerrors the contacts may the interval c "re viii. between one or more its oi the earn.

1g action in normal single ope Thus magni .e error or change in the pressure conditl being maintained.

The initial engagement between the two contacts at the start of each cycle will take place at the high point represented by the cam lobe liifia, and in addition this engagement will usually be of longer duration than the others in the cycle, since the parts of the flat sides I6! of the cam adjacent corner or lobe IEEc are relatively higher than the corresponding portions of the cam sides adjacent the other corners. Thus at the start of each cycle after a change in level has occurred, there may be an appreciable interval of circuit-closing engagement between the contacts, followed by one or more additional intervals of engagement, each of lesser duration and corresponding to the higher of cam lobes 1651) to i'riiih, until the oscillating contact II no longer reaches the contact I4i at the lower 1 high points of the cycle. During this relatively longer inoperative interval, the device will have more opportunity to return to its balanced position as the correcting actions take efifect throughout the system, so that in the next cycle or revolution of the cam, both the number and duration of operative intervals will be decreased, and this diminishing action will continue until balance is restored in the system and the desired level is again established in the vat.

The cycle of cam itii should accordingly be of such duration that under conditions of relatively small variation in the pressure effective on bellows 50, adequate time will be provided between corresponding high points in successive cycles to allow the correcting action or" the first such high point to take effect in the system before the corresponding high point in the next cycle is reached and thus to prevent over-correction. The propor cycle length for a particular installation will thus depend upon the operating condition involved, including particularly the interval required for a correcting action to cause a change in the pressure eiicctive on the control device, and satisfactory results have been obtained with a paper machine of the cylinder type illustrated in Fig. 1 with the cam its rotating at 4 R. P. M. as stated.

It will accordingly be seen that the correcting action of the device will not be continuous iii) but will be intermittent during each revolution of the cam. Also, since the effect of the first circuit-closing engagement between the contacts in each cycle will be felt in the system during the interval represented by the flat side I61 of the cam between the corners 55a and IE5?) and will cause the contact I4I to start to move in the opposite direction, the interval of operative engagement between the two contacts at the next high point in the cycle will be shorter than would be the case if contact MI remained stationary, and so forth until balance is again restored. Thus both the number and the duration of operative intervals of the correcting means in each cycle will vary in accordance with the magnitude of the change in liquid level or other error in the condition to be maintained, to give an aggregate operative interval and an aggregate correcting action which will be in substantially direct proportion to the magnitude of the change or variation from the desired condition as predetermined by the initial adjustment of the device. Furthermore, this precision control will substantially eliminate tendencies toward over-correction and will effectively maintain the liquid level at the desired level with minimum fluctuation.

It will be understood that if the liquid level in the vat decreases, this will cause operation of the control device in similar manner except that the free end of beam I0 willfall and thus cause contacts I and I50 to operate motor 5I through magnetic reversing switch I80 in the proper direction to cause valve 50 to close and thus to decrease the rate of discharge from compartment 20. The device will accordingly function to maintain a desired level within close limits and with substantially micrometer precision. For example, with a bellows B8 of approximately four inches in diameter, the device can be adjusted to respond to variations in liquid level of as little as plus or minus 0.10 inch, and even greater sensitivity can be obtained with a bellows of larger diameter. On the other hand, if it is desired to permit greater variation before correcting action takes place, this may be adjusted for by suitable regulation of the relative spacing of contacts M0 and MI through thumbscrews I to provide for a desired range of movement of beam I0 before either pair of contacts can touch.

In addition to thisprecision control over variations in liquid level during normal operation, this device will also correct for large scale variations such as occur in connection with changes in paper speed or other major adjustments in the system. When such changes occur, the result in the device will be to cause movement of one of contacts I40 or I4I to a position wherein it is in circuit-closing engagement with its associated contact I or I5I throughout one or more complete revolutions of cam I60. Then as conditions approach the desired balance, the device will revent to intermittent operation until the proper level is established. Such major adjustments will necessarily require more time than the operating adjustments described, but this is oifset against the time needed for the other adjustments such as pump speeds in the system, and as soon as the new condition is established the device will continue to maintain it with desired precision. Similar semi-continuous operation of the device may also occur when adjustments are being made to change the level or other condition to be maintained, by relative adjustment of screw III! and weight I20 as described.

While the invention has been described in relation to the maintaining or regulation of a predetermined pressure condition, it is evident that the same system is applicable to the control of other conditions by the making of suitable connections to the pressure developing and balancing mechanism. For example, the motor 5| in Fig. 2 may be connected to operate a rheostat controlling the speed of pump 24 or to operate a suitably located throttling valve as shown in the above referred to Patent 2,347,717, and the pressure responsive bellows may be connected as shown in said patent to the stock inlet passage of a Fourdrinier machine, to respond to the pressure of the stock in the inlet passage and thus to provide for maintaining constant pressure therein. In each case the operation of the device will be the same, with the pairs of contacts I40l50 and Nil-l5! cooperating to regulate the pump speed or stock supply in accordance with changes in the pressure eiiective on the beam '10.

Additionally the device may be arranged as shown in Fig. 2 with the element 56 constructed and arranged to develop pressure on beam 10 in response to changes in a condition such as temperature or humidity. It will therefore be evident that the pressure which is applied to the device may be developed or transmitted in diiferent ways, such as mechanically through fluid means, or the like, with the changes in such condition being used to actuate the control mechamsm.

It should also be noted that the device may be readily arranged to act as a precision measuring device for the pressure effective on the floating beam iii. For such use, the motor 5| may be connected to drive the adjusting screw H0 and thus to cause movement of the weight 20 to correct for deflection of beam 70 caused by variation in the pressure effective thereon and to restore the beam to level position. With this arrangement, the correcting action of the device will be efiective on the adjusting screw with the same precise accuracy and speed as already described in connection with the use of the device for regulating liquid level, and the pointer l2! will accordingly cooperate with a suitably calibrated scale I28 to give a continuously accurate measurement of the pressure effective on the floating beam.

Reference is made to the application of the same inventor, Serial N 0. 7,762, filed of even date herewith and assigned to the same assignee.

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A control device for maintaining a pressure condition within predetermined limits by intermittent operation of control apparatus for regulating said condition including a control circuit, said device comprising a frame, a beam, means pivotally securing one end of said beam to said frame, means responsive to change in said pressure condition for causing pivotal movement of said beam, a pair of relatively movable cooperating contact members for said control circuit, a polygonal cam, means including a drive carried by said fram for mounting said cam for rotation about a predetermined axis, the corners of said cam being arranged at progressively difierent radial distances from said axis around the circumference thereof, means mounting one of said contact members in fixed relation to said frame and in engagement with said cam to cause said member to oscillate in periodic cycles each composed of a plurality of high points of progressively different relative heights corresponding with said corners of said cam and alternating with low points, and means securing the other of said contact members to said beam for movement with said beam relative to said oscillating member.

2. A control device for maintaining a pressure condition within predetermined limits by intermittent operation of control apparatus for regulating said condition including a control circuit, said device comprising a frame, a beam, at bar secured to said beam, a second bar secured to said frame, a Z-shaped spring, means securing one end of said spring to one of said bars and the other end of said spring to the other of said bars, a fiat spring arranged substantially at right angles to said Z-spring opposite substantially the midpoint thereof, means securing said fiat spring to each of said bars, said springs cooperating with said bars to form a pivotal mounting for said beam, means responsive to changes in said pressure condition for causing pivotal movement of said beam, a pair of relatively movable complementary contact members in said control circuit, means securing one of said contact members in fixed relation to said frame, and means securing the other of said contact members to said beam for movement with said beam in response to changes in said pressure condition.

3. In a control device for maintaining a pressure condition within predetermined limits by intermittent operation of control apparatus for regulating said condition, the combination of a control circuit efiective when closed to actuate said regulating means and including a pair of relatively movable cooperating contacts, means including a drive and a cam having a plurality of high points of progressively difierent relative heights alternating with low points for causing controlled relative movement of said contacts in directions to open and close said circuit in accordance with a periodic operating cycle composed of a corresponding plurality of high points of progressively different relative heights alternating with low points, means sensitive to change in said pressure condition, and means associated with said sensitive means and movable in response to change in the pressure effective on said sensitive means to cause further relative movement of said contacts in such direction as to vary the number and duration of the intervals in each said cycle during which said contacts are in circuit-closing relation.

4. In a control device for maintaining a pressure condition within a chamber by intermittent operation of control apparatus for regulating said condition, the combination of pressure sensitive means including a movable member, means providing a pressure connection between said pressure sensitive means and said chamber, means including a control member movable with said movable member for actuating said regulating means in response to changes in pressure within said chamber, and means including a drive and a cam having a plurality of high points of progressively different relative heights alternating with low points for establishing a periodic operating cycle for said actuating means composed of a corresponding plurality of high points of progressively'different relative heights alternating with low points and for varying the number of operative intervals of said actuating means in each said cycle in accordance with the extent or movement of said movable member to provide an aggregate operative interval for said regulating means substantially proportional to the magnitude of change in said pressure.

5. A control device for maintaining a pressure condition within predetermined limits by intermittent operation of control apparatus for regulating said condition including a control circuit, said device comprising a frame, a pair of relatively movable complementary contact members in said control circuit, means for mounting one of said contact members in fixed relation to said frame, means including a drive and a cam having a plurality of high points of progressively different relative heights alternating with low points for causing said fixed member to oscillate in a periodic cycle composed of a corresponding p1urality of high points of progressively different relative heights aiternatn with low points, a pressure sensitive member adapted to be connected with said chamber, means for mounting said pressure sensitive member in said frame, means mounted in said frame and operatively connected with said pressure sensitive member for movement in response to changes in the pressure effective on said'pressure sensitive member, and means securing the other member of said pair of control members to said movable means for movement therewith with respect to said oscillating member in response to changes in "the pressure effective on said pressure sensitive means.

' 6. A control device for maintaining a pressure condition within predetermined limits by intermittent operation of control apparatus for regulating said condition including a pair of selectively operable control circuits, said device comprising a'frame, a pair of relatively movable complementary contact members controlling each said circuit, a polygonal cam, means including a drive carried by said frame for mounting said cam for rotation about a predetermined axis, the corners of said cam being arranged at progressively different radial distances from said axis, means mounting one of said members in each said pair of contact members in fixed relation to said frame and in engagement with said cam to cause said fixed members to oscillate in periodic cycles composed of a plurality of high points of progressively different relative heights corresponding with said corners of said cam and alternating with low points, a pressure sensitive member mounted in said frame and adapted to be placed in pressure connection with said chamber, a member mounted for movement in response to change inthe' pressure effective on said pressure sensitive member, and means connecting the other members of each said pair of contact members to said movable member for movement therewith with respect to said oscillating contact members in response to changes in the pressure effective on said pressure sensitive member.

'7. A control device for maintaining a pressure condition within predetermined limits by intermittent operation of control apparatus for regulating said condition, said device comprising a frame, means for sensing changes in said pressure condition includin a part supported on said frame for movement in response to such pressure change, actuating means for said control apparatus including complementary contact members carried by said frame and said movable part re-' speotively for coaction to operate said control apparatus in response to movement or" said movable part, and drive means including a cam having a plurality of high points of progressively different relative heights alternating with low points for establishing a periodic operating cycle for said actuating means in order to vary the number and duration of intervals of coaction of said contact members during each said cycle in accordance with the magnitude of changes in said condition and the resulting movement of said movable part to provide an aggregate operative interval for said control apparatus substantially proportional to the magnitude of said changes.

8. A control device for maintaining a pressure condition within predetermined limits by intermittent operation of control apparatus for regulating said condition inciuding a control circuit, said device comprising a frame, means for sensing changes in said pressure condition including a part supported on said frame for movement in response to such change, control means for said control circuit including a pair of relatively movable complementary contact members, means supporting one or said contact members on said frame, means supporting one said contact member for movement with said movable part with I respect to said frame and drive means including a cam having a plurality of high points of pregressively different relative heights alternating with low points for causing movement of the other said contact member in periodic cycles each composed of a corresponding plurality of high points of progressively difierent relative heights alternating with low points in order to effect coaction of said contact members and operation of said control apparatus thereby in response to movement of said movable part and to vary the numoer and duration of the intervals of coaction of said contact members during each said cycle in direct relation with the magnitude of said changes in said pressure condition.

9. A control device for maintaining a pressure condition within predetermined limits by intermittent operation of control apparatus for regulating said condition including a control circuit effective when closed to cause operation of said regulating apparatus, said device comprising a frame, means for sensing changes in said pressure condition including a part supported on said frame for movement in response to such pressure change, a pair of relatively movable complementary contact members for controlling said circuit, drive means on said frame including a cam having a plurality of high points of progressively different relative heights alternating with low points for continuously moving one of said contact members toward and away from the other said contact member in a periodic operating cycle including a corresponding plurality of spaced high points of different heights alternating with a plurality of lower points, means supporting the other said contact member for movement with said movable part with respect to said one contact member, means for adjusting the position of said movable part to maintain said contact member thereon out of contact with said periodically moving contact member While said pressure condition is maintained within said limits, and means for causing said movable memher to carry said contact member thereon towards said periodically moving contact member in re sponse to change in said pressure condition to 15 effect ccaction of said contact members and corresponding operation of said control apparatus.

10. A control device for maintaining a pressure condition Within predetermined limits by intermittent operation of control apparatus for regulating said condition including a control circuit, said device comprising a frame, a pair of relatively movable complementary contact members controlling said circuit, means on said frame for causing one of said contact members to oscillate in a periodic cycle composed of a plurality of low and high points, said high points in said cycle being of progressively different relative heights, means for sensing changes in said pressure condition including a part supported on said frame for movement in response to such pressure change, said other contact member being carried by said movable part for movement therewith towards and away from said oscillating contact member in response to changes in said pressure condition, and adjustable means for establishing a neutral position of said sensing means and said movable part maintaining said contact members out of contact when said pressure condition is within said predetermined limits.

11. A control device for maintaining a pressure condition within predetermined limits by intermittent operation of control apparatus for regulating said condition including a pair of selectively operable control circuits, said device comprising a frame, a pair of relatively movabl complementary contact members controlling each of said circuits, means on said frame for causing one of said contact members of each said pair thereof to oscillate in a periodic cycle composed of a plurality of alternate high and low points, said high points in said cycle being of progressively different relative heights, means for sensing changes in said pressure condition including a part supported on said frame for movement in response taining each said pair of contact members out of contact with each other when said pressure condition is within said predetermined limits.

12. A control device for maintaining a pressure condition within predetermined limits by intermittent operation of control apparatus for regulating said condition including a control circuit, said device comprising a frame, a pair of relatively movable complementary contact members controlling said circuit, a polygonal cam mounted on said frame for rotation about a predetermined axis, a drive for continuously rotating said cam about said axis, the corners of said cam being arranged at progressively different radial distances from said axis, means on said frame supporting one of said contact members in driven engagement with said cam to cause said contact member to oscillat in a periodic cycle composed of a plurality of high points of progressively different relative heights corresponding with said corners of said cam and alternating with low points, means for sensing changes in said pressure condition includin a part supported on said frame for movement in response to such pressure change, said other contact member being carried by said movabl part for movement therewith towards and away from said oscillating contact member in response to changes in said pressure 16 condition, and adjustable means for establishing a neutral position of said sensing means and said movable part maintaining said contact members out of contact when said pressure condition is within said predetermined limits.

13. A control device for maintaining a pressure condition within predetermined limits by intermittent operation of control apparatus for regulating said condition including a pair of selectively operable control circuits, said device comprising a frame, a pair of relatively movable complementary contact members controlling each of said circuits, a polygonal cam mounted on said frame for movement about a predetermined axis, a drive for continuously rotating said cam about said axis, the corners of said cam being arranged at progressively different radial distances at said axis, means on said frame supporting one of said contact members of each said pair in driving engagement with said cam to cause said members to oscillate in periodic cycles each composed of a plurality of high points of progressively different relative heights corresponding with said corners of said cam and alternating with low points, means for sensing changes in said pressure condition including a part supported on said frame for movement in response to such pressure change, said other contact member of each said pair being carried by said movable part for movement therewith with respect to said oscillating contact members in response to changes in said pressure condition, and adjustable means for establishing a neutral position of said sensing means and said movable part maintaining each said pair of contact members out of contact with each other when said pressure condition is within said predetermined limits.

14. A control device for maintaining a pressure condition within predetermined limits by intermittent operation of control apparatus for regulating said condition including a pair of selectively operabl control circuits, said device comprising a frame, a beam, means pivotally mounting said beam in said frame, means for sensing changes in said pressure condition, an operative connection between said sensing means and said beam for causing movement of said beam about said pivotal mounting in response to such pressure changes, a separate pair of relatively movable cooperating contact members in each of said control circuits, means for mounting one of said members in each said pair in fixed relation to said frame, means including a drive and a cam having a plurality of high points of progressively different relative heights alternating with low points for causing each of said fixed contact members to oscillate in a cycle composed of a corresponding plurality of spaced high points of progressively different heights alternating with low points, and means supporting the other contact member of each said pair on said beam for movement therewith with respect to said oscillating contact members.

STEPHEN A. STAEGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

